Peroxygen compounds are useful in many applications that require enhanced oxidation. The effectiveness of peroxygen compounds as oxidizers depend partly on their rate of decomposition, which in turn depends on environmental factors. For example, if the environment contains elements that increase the decomposition rate of peroxygen compounds such as high humidity, mixing, and exposure to incompatible chemicals, the effectiveness of the peroxygen compounds is compromised.
Potassium monopersulfate (PMPS) is a peroxygen compound that is recognized for its high oxidizing potential. PMPS effectivey oxidizes organics even when other peroxygen compounds, such as hydrogen peroxide, are either less effective or not effective at all. For example, PMPS is capable of oxidizing complex organics such as lignin and tannin in paper and stains/dyes in clothes, neither of which is easily removable with hydrogen peroxide.
PMPS has the ability to convert halogens such as chloride ions into sanitizers such as chlorine gas, hypochlorous acid, and hypochorite ions. Thus, PMPS is often applied in conjunction with halogen donors and/or other oxidizers to achieve optimal effect.
While PMPS is a very desirable oxidizer with a broad range of beneficial applications, its use is either limited or altogether restricted due to the presence of impurities such as the harsh irritant potassium oxodisulfate (K2S2O8), also commonly referred to as potassium persulfate. Numerous medical and dermatological studies have documented the effects of K2S2O8 resulting from direct or indirect contact with the irritant. For example, irritation associated with residual K2S2O8 on dentures has been linked to allergic reactions and oral discomfort. Hair loss and severe dermatitis of the scalp have occurred from contact with oxodisulfate present in hair dyes. A wide range of medical symptoms have been directly linked to airborne inhalation as well as direct and indirect (residual) contact from agents containing oxodisulfate. Bathers have reported rash formation and, in some cases, severe lesions as a result of bathing in swimming pools where products containing oxodisulfate had been used. More details regarding effects of oxodisufate are documented in the following references:                Le Coz C J, Bezard M., “Allergic contact cheilitis due to effervescent dental cleanser: combined responsibilities of the allergen persulfate and prosthesis porosity.” Contact Dermatitis, Vol. 41(5): 268-71 (November 1999). Consultation de Dermato-Allergologie, Clinique Dermatologique des Hopitaux Universitaires de Strasbourg 1, France.        Yawalkar N, Helbling A, et al., “T cell involvement in persulfate triggered occupational contact dermatitis and asthma.” Ann Allergy Asthma Immunol., Vol. 82(4):401-4 (April 1999), Institute of Immunology and Allergology, University of Bern, Inselspital, Switzerland.        “Contact urticaria due to potassium persulfate,” Contact Dermatitis, 2001 September 45(3):177. PMID: 11553153 [PubMed—indexed for MEDLINE]        
PMPS formulations have also been limited in their application due to its instability and/or reactivity with other compounds such as moisture, organics, halogens and the like, encountered when formulated with various compounds and/or exposed to various environments.
Thus, in order to effectively exploit the oxidizing power of a peroxygen compound, the chemistry of the peroxygen compound and the elements it would be exposed to in a particular application must be carefully considered. The peroxygen compound's rate of dissolution, the level of humidity in the environment, and the peroxygen compound's incompatibility with certain substances (e.g., alkali versus acid) are among some of the factors to be considered. Considering these factors, a coating is sometimes used with the PMPS. The coating itself must be compatible with the PMPS composition and have preferably hypoallergenic characteristics to enhance the utility of PMPS.
One way to lower the effects of peroxygen compounds' sensitivity involves coating or treating the compound to shield it from elements that cause its decomposition. For example, sodium percarbonate and sodium perborate are sometimes treated with coatings to enhance their utility.
Particles of peroxygen compounds may be coated with various substances, some of which include trona (U.S. Pat. No. 4,105,827), sodium silicate (U.S. Pat. No. 3,951,838), sodium perborate plus sodium silicate (U.S. Pat. No. 4,194,025), boric acid (U.S. Pat. No. 4,321,301), wax (U.S. Pat. No. 4,421,669), a polymer latex (U.S. Pat. No. 4,759,956), sodium silicate plus a chelate (U.S. Pat. No. 4,126, 717), sodium borosilicate (U.S. Pat. No. 5,194,176). Generally, these treatments show some improvement in stability in a humid environment of alkaline percarbonates and perborates. In general, these coating processes are based on either 1) physically coating the sodium percarbonate with a compound such as trona, boric acid, and the like to act as a spacer and prevent the percarbonate from physically contacting the other compounds in the detergent composition, or 2) coating the peroxygen compound with a vapor barrier such as a wax or a polymer.
However, none of these coating materials have successfully stabilized the peroxide compound because it is usually a matter of time until water vapor penetrates the physical barrier and initiates decomposition. If a vapor-impervious barrier is used, the rate of dissolution of the peroxide particle is retarded so much so that the compound is no longer useful.
What is desired is a method of coating a peroxygen compound so that it does not decompose before use but in a way that the coating does not interfere with the effect of the peroxygen compound during use.